sched/headers: Prepare for the removal of <linux/rtmutex.h> from <linux/sched.h>

[mirror_ubuntu-artful-kernel.git] / include / linux / i2c.h

/* ------------------------------------------------------------------------- */
/*                                                                           */
/* i2c.h - definitions for the i2c-bus interface                             */
/*                                                                           */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-2000 Simon G. Vogl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
    MA 02110-1301 USA.                                                       */
/* ------------------------------------------------------------------------- */

/* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and
   Frodo Looijaard <frodol@dds.nl> */
#ifndef _LINUX_I2C_H
#define _LINUX_I2C_H

#include <linux/mod_devicetable.h>
#include <linux/device.h>       /* for struct device */
#include <linux/sched.h>        /* for completion */
#include <linux/mutex.h>
#include <linux/rtmutex.h>
#include <linux/irqdomain.h>            /* for Host Notify IRQ */
#include <linux/of.h>           /* for struct device_node */
#include <linux/swab.h>         /* for swab16 */
#include <uapi/linux/i2c.h>

extern struct bus_type i2c_bus_type;
extern struct device_type i2c_adapter_type;

/* --- General options ------------------------------------------------ */

struct i2c_msg;
struct i2c_algorithm;
struct i2c_adapter;
struct i2c_client;
struct i2c_driver;
union i2c_smbus_data;
struct i2c_board_info;
enum i2c_slave_event;
typedef int (*i2c_slave_cb_t)(struct i2c_client *, enum i2c_slave_event, u8 *);

struct module;
struct property_entry;

#if defined(CONFIG_I2C) || defined(CONFIG_I2C_MODULE)
/*
 * The master routines are the ones normally used to transmit data to devices
 * on a bus (or read from them). Apart from two basic transfer functions to
 * transmit one message at a time, a more complex version can be used to
 * transmit an arbitrary number of messages without interruption.
 * @count must be be less than 64k since msg.len is u16.
 */
extern int i2c_master_send(const struct i2c_client *client, const char *buf,
                           int count);
extern int i2c_master_recv(const struct i2c_client *client, char *buf,
                           int count);

/* Transfer num messages.
 */
extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                        int num);
/* Unlocked flavor */
extern int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                          int num);

/* This is the very generalized SMBus access routine. You probably do not
   want to use this, though; one of the functions below may be much easier,
   and probably just as fast.
   Note that we use i2c_adapter here, because you do not need a specific
   smbus adapter to call this function. */
extern s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
                          unsigned short flags, char read_write, u8 command,
                          int size, union i2c_smbus_data *data);

/* Now follow the 'nice' access routines. These also document the calling
   conventions of i2c_smbus_xfer. */

extern s32 i2c_smbus_read_byte(const struct i2c_client *client);
extern s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value);
extern s32 i2c_smbus_read_byte_data(const struct i2c_client *client,
                                    u8 command);
extern s32 i2c_smbus_write_byte_data(const struct i2c_client *client,
                                     u8 command, u8 value);
extern s32 i2c_smbus_read_word_data(const struct i2c_client *client,
                                    u8 command);
extern s32 i2c_smbus_write_word_data(const struct i2c_client *client,
                                     u8 command, u16 value);

static inline s32
i2c_smbus_read_word_swapped(const struct i2c_client *client, u8 command)
{
        s32 value = i2c_smbus_read_word_data(client, command);

        return (value < 0) ? value : swab16(value);
}

static inline s32
i2c_smbus_write_word_swapped(const struct i2c_client *client,
                             u8 command, u16 value)
{
        return i2c_smbus_write_word_data(client, command, swab16(value));
}

/* Returns the number of read bytes */
extern s32 i2c_smbus_read_block_data(const struct i2c_client *client,
                                     u8 command, u8 *values);
extern s32 i2c_smbus_write_block_data(const struct i2c_client *client,
                                      u8 command, u8 length, const u8 *values);
/* Returns the number of read bytes */
extern s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,
                                         u8 command, u8 length, u8 *values);
extern s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,
                                          u8 command, u8 length,
                                          const u8 *values);
extern s32
i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
                                          u8 command, u8 length, u8 *values);
#endif /* I2C */

enum i2c_alert_protocol {
        I2C_PROTOCOL_SMBUS_ALERT,
        I2C_PROTOCOL_SMBUS_HOST_NOTIFY,
};

/**
 * struct i2c_driver - represent an I2C device driver
 * @class: What kind of i2c device we instantiate (for detect)
 * @attach_adapter: Callback for bus addition (deprecated)
 * @probe: Callback for device binding - soon to be deprecated
 * @probe_new: New callback for device binding
 * @remove: Callback for device unbinding
 * @shutdown: Callback for device shutdown
 * @alert: Alert callback, for example for the SMBus alert protocol
 * @command: Callback for bus-wide signaling (optional)
 * @driver: Device driver model driver
 * @id_table: List of I2C devices supported by this driver
 * @detect: Callback for device detection
 * @address_list: The I2C addresses to probe (for detect)
 * @clients: List of detected clients we created (for i2c-core use only)
 *
 * The driver.owner field should be set to the module owner of this driver.
 * The driver.name field should be set to the name of this driver.
 *
 * For automatic device detection, both @detect and @address_list must
 * be defined. @class should also be set, otherwise only devices forced
 * with module parameters will be created. The detect function must
 * fill at least the name field of the i2c_board_info structure it is
 * handed upon successful detection, and possibly also the flags field.
 *
 * If @detect is missing, the driver will still work fine for enumerated
 * devices. Detected devices simply won't be supported. This is expected
 * for the many I2C/SMBus devices which can't be detected reliably, and
 * the ones which can always be enumerated in practice.
 *
 * The i2c_client structure which is handed to the @detect callback is
 * not a real i2c_client. It is initialized just enough so that you can
 * call i2c_smbus_read_byte_data and friends on it. Don't do anything
 * else with it. In particular, calling dev_dbg and friends on it is
 * not allowed.
 */
struct i2c_driver {
        unsigned int class;

        /* Notifies the driver that a new bus has appeared. You should avoid
         * using this, it will be removed in a near future.
         */
        int (*attach_adapter)(struct i2c_adapter *) __deprecated;

        /* Standard driver model interfaces */
        int (*probe)(struct i2c_client *, const struct i2c_device_id *);
        int (*remove)(struct i2c_client *);

        /* New driver model interface to aid the seamless removal of the
         * current probe()'s, more commonly unused than used second parameter.
         */
        int (*probe_new)(struct i2c_client *);

        /* driver model interfaces that don't relate to enumeration  */
        void (*shutdown)(struct i2c_client *);

        /* Alert callback, for example for the SMBus alert protocol.
         * The format and meaning of the data value depends on the protocol.
         * For the SMBus alert protocol, there is a single bit of data passed
         * as the alert response's low bit ("event flag").
         * For the SMBus Host Notify protocol, the data corresponds to the
         * 16-bit payload data reported by the slave device acting as master.
         */
        void (*alert)(struct i2c_client *, enum i2c_alert_protocol protocol,
                      unsigned int data);

        /* a ioctl like command that can be used to perform specific functions
         * with the device.
         */
        int (*command)(struct i2c_client *client, unsigned int cmd, void *arg);

        struct device_driver driver;
        const struct i2c_device_id *id_table;

        /* Device detection callback for automatic device creation */
        int (*detect)(struct i2c_client *, struct i2c_board_info *);
        const unsigned short *address_list;
        struct list_head clients;
};
#define to_i2c_driver(d) container_of(d, struct i2c_driver, driver)

/**
 * struct i2c_client - represent an I2C slave device
 * @flags: I2C_CLIENT_TEN indicates the device uses a ten bit chip address;
 *      I2C_CLIENT_PEC indicates it uses SMBus Packet Error Checking
 * @addr: Address used on the I2C bus connected to the parent adapter.
 * @name: Indicates the type of the device, usually a chip name that's
 *      generic enough to hide second-sourcing and compatible revisions.
 * @adapter: manages the bus segment hosting this I2C device
 * @dev: Driver model device node for the slave.
 * @irq: indicates the IRQ generated by this device (if any)
 * @detected: member of an i2c_driver.clients list or i2c-core's
 *      userspace_devices list
 * @slave_cb: Callback when I2C slave mode of an adapter is used. The adapter
 *      calls it to pass on slave events to the slave driver.
 *
 * An i2c_client identifies a single device (i.e. chip) connected to an
 * i2c bus. The behaviour exposed to Linux is defined by the driver
 * managing the device.
 */
struct i2c_client {
        unsigned short flags;           /* div., see below              */
        unsigned short addr;            /* chip address - NOTE: 7bit    */
                                        /* addresses are stored in the  */
                                        /* _LOWER_ 7 bits               */
        char name[I2C_NAME_SIZE];
        struct i2c_adapter *adapter;    /* the adapter we sit on        */
        struct device dev;              /* the device structure         */
        int irq;                        /* irq issued by device         */
        struct list_head detected;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        i2c_slave_cb_t slave_cb;        /* callback for slave mode      */
#endif
};
#define to_i2c_client(d) container_of(d, struct i2c_client, dev)

extern struct i2c_client *i2c_verify_client(struct device *dev);
extern struct i2c_adapter *i2c_verify_adapter(struct device *dev);
extern const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
                                        const struct i2c_client *client);

static inline struct i2c_client *kobj_to_i2c_client(struct kobject *kobj)
{
        struct device * const dev = container_of(kobj, struct device, kobj);
        return to_i2c_client(dev);
}

static inline void *i2c_get_clientdata(const struct i2c_client *dev)
{
        return dev_get_drvdata(&dev->dev);
}

static inline void i2c_set_clientdata(struct i2c_client *dev, void *data)
{
        dev_set_drvdata(&dev->dev, data);
}

/* I2C slave support */

#if IS_ENABLED(CONFIG_I2C_SLAVE)
enum i2c_slave_event {
        I2C_SLAVE_READ_REQUESTED,
        I2C_SLAVE_WRITE_REQUESTED,
        I2C_SLAVE_READ_PROCESSED,
        I2C_SLAVE_WRITE_RECEIVED,
        I2C_SLAVE_STOP,
};

extern int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb);
extern int i2c_slave_unregister(struct i2c_client *client);
extern bool i2c_detect_slave_mode(struct device *dev);

static inline int i2c_slave_event(struct i2c_client *client,
                                  enum i2c_slave_event event, u8 *val)
{
        return client->slave_cb(client, event, val);
}
#endif

/**
 * struct i2c_board_info - template for device creation
 * @type: chip type, to initialize i2c_client.name
 * @flags: to initialize i2c_client.flags
 * @addr: stored in i2c_client.addr
 * @platform_data: stored in i2c_client.dev.platform_data
 * @archdata: copied into i2c_client.dev.archdata
 * @of_node: pointer to OpenFirmware device node
 * @fwnode: device node supplied by the platform firmware
 * @properties: additional device properties for the device
 * @irq: stored in i2c_client.irq
 *
 * I2C doesn't actually support hardware probing, although controllers and
 * devices may be able to use I2C_SMBUS_QUICK to tell whether or not there's
 * a device at a given address.  Drivers commonly need more information than
 * that, such as chip type, configuration, associated IRQ, and so on.
 *
 * i2c_board_info is used to build tables of information listing I2C devices
 * that are present.  This information is used to grow the driver model tree.
 * For mainboards this is done statically using i2c_register_board_info();
 * bus numbers identify adapters that aren't yet available.  For add-on boards,
 * i2c_new_device() does this dynamically with the adapter already known.
 */
struct i2c_board_info {
        char            type[I2C_NAME_SIZE];
        unsigned short  flags;
        unsigned short  addr;
        void            *platform_data;
        struct dev_archdata     *archdata;
        struct device_node *of_node;
        struct fwnode_handle *fwnode;
        const struct property_entry *properties;
        int             irq;
};

/**
 * I2C_BOARD_INFO - macro used to list an i2c device and its address
 * @dev_type: identifies the device type
 * @dev_addr: the device's address on the bus.
 *
 * This macro initializes essential fields of a struct i2c_board_info,
 * declaring what has been provided on a particular board.  Optional
 * fields (such as associated irq, or device-specific platform_data)
 * are provided using conventional syntax.
 */
#define I2C_BOARD_INFO(dev_type, dev_addr) \
        .type = dev_type, .addr = (dev_addr)


#if defined(CONFIG_I2C) || defined(CONFIG_I2C_MODULE)
/* Add-on boards should register/unregister their devices; e.g. a board
 * with integrated I2C, a config eeprom, sensors, and a codec that's
 * used in conjunction with the primary hardware.
 */
extern struct i2c_client *
i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info);

/* If you don't know the exact address of an I2C device, use this variant
 * instead, which can probe for device presence in a list of possible
 * addresses. The "probe" callback function is optional. If it is provided,
 * it must return 1 on successful probe, 0 otherwise. If it is not provided,
 * a default probing method is used.
 */
extern struct i2c_client *
i2c_new_probed_device(struct i2c_adapter *adap,
                      struct i2c_board_info *info,
                      unsigned short const *addr_list,
                      int (*probe)(struct i2c_adapter *, unsigned short addr));

/* Common custom probe functions */
extern int i2c_probe_func_quick_read(struct i2c_adapter *, unsigned short addr);

/* For devices that use several addresses, use i2c_new_dummy() to make
 * client handles for the extra addresses.
 */
extern struct i2c_client *
i2c_new_dummy(struct i2c_adapter *adap, u16 address);

extern struct i2c_client *
i2c_new_secondary_device(struct i2c_client *client,
                                const char *name,
                                u16 default_addr);

extern void i2c_unregister_device(struct i2c_client *);
#endif /* I2C */

/* Mainboard arch_initcall() code should register all its I2C devices.
 * This is done at arch_initcall time, before declaring any i2c adapters.
 * Modules for add-on boards must use other calls.
 */
#ifdef CONFIG_I2C_BOARDINFO
extern int
i2c_register_board_info(int busnum, struct i2c_board_info const *info,
                        unsigned n);
#else
static inline int
i2c_register_board_info(int busnum, struct i2c_board_info const *info,
                        unsigned n)
{
        return 0;
}
#endif /* I2C_BOARDINFO */

/**
 * struct i2c_algorithm - represent I2C transfer method
 * @master_xfer: Issue a set of i2c transactions to the given I2C adapter
 *   defined by the msgs array, with num messages available to transfer via
 *   the adapter specified by adap.
 * @smbus_xfer: Issue smbus transactions to the given I2C adapter. If this
 *   is not present, then the bus layer will try and convert the SMBus calls
 *   into I2C transfers instead.
 * @functionality: Return the flags that this algorithm/adapter pair supports
 *   from the I2C_FUNC_* flags.
 * @reg_slave: Register given client to I2C slave mode of this adapter
 * @unreg_slave: Unregister given client from I2C slave mode of this adapter
 *
 * The following structs are for those who like to implement new bus drivers:
 * i2c_algorithm is the interface to a class of hardware solutions which can
 * be addressed using the same bus algorithms - i.e. bit-banging or the PCF8584
 * to name two of the most common.
 *
 * The return codes from the @master_xfer field should indicate the type of
 * error code that occurred during the transfer, as documented in the kernel
 * Documentation file Documentation/i2c/fault-codes.
 */
struct i2c_algorithm {
        /* If an adapter algorithm can't do I2C-level access, set master_xfer
           to NULL. If an adapter algorithm can do SMBus access, set
           smbus_xfer. If set to NULL, the SMBus protocol is simulated
           using common I2C messages */
        /* master_xfer should return the number of messages successfully
           processed, or a negative value on error */
        int (*master_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs,
                           int num);
        int (*smbus_xfer) (struct i2c_adapter *adap, u16 addr,
                           unsigned short flags, char read_write,
                           u8 command, int size, union i2c_smbus_data *data);

        /* To determine what the adapter supports */
        u32 (*functionality) (struct i2c_adapter *);

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        int (*reg_slave)(struct i2c_client *client);
        int (*unreg_slave)(struct i2c_client *client);
#endif
};

/**
 * struct i2c_lock_operations - represent I2C locking operations
 * @lock_bus: Get exclusive access to an I2C bus segment
 * @trylock_bus: Try to get exclusive access to an I2C bus segment
 * @unlock_bus: Release exclusive access to an I2C bus segment
 *
 * The main operations are wrapped by i2c_lock_bus and i2c_unlock_bus.
 */
struct i2c_lock_operations {
        void (*lock_bus)(struct i2c_adapter *, unsigned int flags);
        int (*trylock_bus)(struct i2c_adapter *, unsigned int flags);
        void (*unlock_bus)(struct i2c_adapter *, unsigned int flags);
};

/**
 * struct i2c_timings - I2C timing information
 * @bus_freq_hz: the bus frequency in Hz
 * @scl_rise_ns: time SCL signal takes to rise in ns; t(r) in the I2C specification
 * @scl_fall_ns: time SCL signal takes to fall in ns; t(f) in the I2C specification
 * @scl_int_delay_ns: time IP core additionally needs to setup SCL in ns
 * @sda_fall_ns: time SDA signal takes to fall in ns; t(f) in the I2C specification
 */
struct i2c_timings {
        u32 bus_freq_hz;
        u32 scl_rise_ns;
        u32 scl_fall_ns;
        u32 scl_int_delay_ns;
        u32 sda_fall_ns;
};

/**
 * struct i2c_bus_recovery_info - I2C bus recovery information
 * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or
 *      i2c_generic_scl_recovery() or i2c_generic_gpio_recovery().
 * @get_scl: This gets current value of SCL line. Mandatory for generic SCL
 *      recovery. Used internally for generic GPIO recovery.
 * @set_scl: This sets/clears SCL line. Mandatory for generic SCL recovery. Used
 *      internally for generic GPIO recovery.
 * @get_sda: This gets current value of SDA line. Optional for generic SCL
 *      recovery. Used internally, if sda_gpio is a valid GPIO, for generic GPIO
 *      recovery.
 * @prepare_recovery: This will be called before starting recovery. Platform may
 *      configure padmux here for SDA/SCL line or something else they want.
 * @unprepare_recovery: This will be called after completing recovery. Platform
 *      may configure padmux here for SDA/SCL line or something else they want.
 * @scl_gpio: gpio number of the SCL line. Only required for GPIO recovery.
 * @sda_gpio: gpio number of the SDA line. Only required for GPIO recovery.
 */
struct i2c_bus_recovery_info {
        int (*recover_bus)(struct i2c_adapter *);

        int (*get_scl)(struct i2c_adapter *);
        void (*set_scl)(struct i2c_adapter *, int val);
        int (*get_sda)(struct i2c_adapter *);

        void (*prepare_recovery)(struct i2c_adapter *);
        void (*unprepare_recovery)(struct i2c_adapter *);

        /* gpio recovery */
        int scl_gpio;
        int sda_gpio;
};

int i2c_recover_bus(struct i2c_adapter *adap);

/* Generic recovery routines */
int i2c_generic_gpio_recovery(struct i2c_adapter *adap);
int i2c_generic_scl_recovery(struct i2c_adapter *adap);

/**
 * struct i2c_adapter_quirks - describe flaws of an i2c adapter
 * @flags: see I2C_AQ_* for possible flags and read below
 * @max_num_msgs: maximum number of messages per transfer
 * @max_write_len: maximum length of a write message
 * @max_read_len: maximum length of a read message
 * @max_comb_1st_msg_len: maximum length of the first msg in a combined message
 * @max_comb_2nd_msg_len: maximum length of the second msg in a combined message
 *
 * Note about combined messages: Some I2C controllers can only send one message
 * per transfer, plus something called combined message or write-then-read.
 * This is (usually) a small write message followed by a read message and
 * barely enough to access register based devices like EEPROMs. There is a flag
 * to support this mode. It implies max_num_msg = 2 and does the length checks
 * with max_comb_*_len because combined message mode usually has its own
 * limitations. Because of HW implementations, some controllers can actually do
 * write-then-anything or other variants. To support that, write-then-read has
 * been broken out into smaller bits like write-first and read-second which can
 * be combined as needed.
 */

struct i2c_adapter_quirks {
        u64 flags;
        int max_num_msgs;
        u16 max_write_len;
        u16 max_read_len;
        u16 max_comb_1st_msg_len;
        u16 max_comb_2nd_msg_len;
};

/* enforce max_num_msgs = 2 and use max_comb_*_len for length checks */
#define I2C_AQ_COMB                     BIT(0)
/* first combined message must be write */
#define I2C_AQ_COMB_WRITE_FIRST         BIT(1)
/* second combined message must be read */
#define I2C_AQ_COMB_READ_SECOND         BIT(2)
/* both combined messages must have the same target address */
#define I2C_AQ_COMB_SAME_ADDR           BIT(3)
/* convenience macro for typical write-then read case */
#define I2C_AQ_COMB_WRITE_THEN_READ     (I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST | \
                                         I2C_AQ_COMB_READ_SECOND | I2C_AQ_COMB_SAME_ADDR)
/* clock stretching is not supported */
#define I2C_AQ_NO_CLK_STRETCH           BIT(4)

/*
 * i2c_adapter is the structure used to identify a physical i2c bus along
 * with the access algorithms necessary to access it.
 */
struct i2c_adapter {
        struct module *owner;
        unsigned int class;               /* classes to allow probing for */
        const struct i2c_algorithm *algo; /* the algorithm to access the bus */
        void *algo_data;

        /* data fields that are valid for all devices   */
        const struct i2c_lock_operations *lock_ops;
        struct rt_mutex bus_lock;
        struct rt_mutex mux_lock;

        int timeout;                    /* in jiffies */
        int retries;
        struct device dev;              /* the adapter device */

        int nr;
        char name[48];
        struct completion dev_released;

        struct mutex userspace_clients_lock;
        struct list_head userspace_clients;

        struct i2c_bus_recovery_info *bus_recovery_info;
        const struct i2c_adapter_quirks *quirks;

        struct irq_domain *host_notify_domain;
};
#define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)

static inline void *i2c_get_adapdata(const struct i2c_adapter *dev)
{
        return dev_get_drvdata(&dev->dev);
}

static inline void i2c_set_adapdata(struct i2c_adapter *dev, void *data)
{
        dev_set_drvdata(&dev->dev, data);
}

static inline struct i2c_adapter *
i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter)
{
#if IS_ENABLED(CONFIG_I2C_MUX)
        struct device *parent = adapter->dev.parent;

        if (parent != NULL && parent->type == &i2c_adapter_type)
                return to_i2c_adapter(parent);
        else
#endif
                return NULL;
}

int i2c_for_each_dev(void *data, int (*fn)(struct device *, void *));

/* Adapter locking functions, exported for shared pin cases */
#define I2C_LOCK_ROOT_ADAPTER BIT(0)
#define I2C_LOCK_SEGMENT      BIT(1)

/**
 * i2c_lock_bus - Get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER locks the root i2c adapter, I2C_LOCK_SEGMENT
 *      locks only this branch in the adapter tree
 */
static inline void
i2c_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        adapter->lock_ops->lock_bus(adapter, flags);
}

/**
 * i2c_trylock_bus - Try to get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER tries to locks the root i2c adapter,
 *      I2C_LOCK_SEGMENT tries to lock only this branch in the adapter tree
 *
 * Return: true if the I2C bus segment is locked, false otherwise
 */
static inline int
i2c_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        return adapter->lock_ops->trylock_bus(adapter, flags);
}

/**
 * i2c_unlock_bus - Release exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER unlocks the root i2c adapter, I2C_LOCK_SEGMENT
 *      unlocks only this branch in the adapter tree
 */
static inline void
i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        adapter->lock_ops->unlock_bus(adapter, flags);
}

static inline void
i2c_lock_adapter(struct i2c_adapter *adapter)
{
        i2c_lock_bus(adapter, I2C_LOCK_ROOT_ADAPTER);
}

static inline void
i2c_unlock_adapter(struct i2c_adapter *adapter)
{
        i2c_unlock_bus(adapter, I2C_LOCK_ROOT_ADAPTER);
}

/*flags for the client struct: */
#define I2C_CLIENT_PEC          0x04    /* Use Packet Error Checking */
#define I2C_CLIENT_TEN          0x10    /* we have a ten bit chip address */
                                        /* Must equal I2C_M_TEN below */
#define I2C_CLIENT_SLAVE        0x20    /* we are the slave */
#define I2C_CLIENT_HOST_NOTIFY  0x40    /* We want to use I2C host notify */
#define I2C_CLIENT_WAKE         0x80    /* for board_info; true iff can wake */
#define I2C_CLIENT_SCCB         0x9000  /* Use Omnivision SCCB protocol */
                                        /* Must match I2C_M_STOP|IGNORE_NAK */

/* i2c adapter classes (bitmask) */
#define I2C_CLASS_HWMON         (1<<0)  /* lm_sensors, ... */
#define I2C_CLASS_DDC           (1<<3)  /* DDC bus on graphics adapters */
#define I2C_CLASS_SPD           (1<<7)  /* Memory modules */
#define I2C_CLASS_DEPRECATED    (1<<8)  /* Warn users that adapter will stop using classes */

/* Internal numbers to terminate lists */
#define I2C_CLIENT_END          0xfffeU

/* Construct an I2C_CLIENT_END-terminated array of i2c addresses */
#define I2C_ADDRS(addr, addrs...) \
        ((const unsigned short []){ addr, ## addrs, I2C_CLIENT_END })


/* ----- functions exported by i2c.o */

/* administration...
 */
#if defined(CONFIG_I2C) || defined(CONFIG_I2C_MODULE)
extern int i2c_add_adapter(struct i2c_adapter *);
extern void i2c_del_adapter(struct i2c_adapter *);
extern int i2c_add_numbered_adapter(struct i2c_adapter *);

extern int i2c_register_driver(struct module *, struct i2c_driver *);
extern void i2c_del_driver(struct i2c_driver *);

/* use a define to avoid include chaining to get THIS_MODULE */
#define i2c_add_driver(driver) \
        i2c_register_driver(THIS_MODULE, driver)

extern struct i2c_client *i2c_use_client(struct i2c_client *client);
extern void i2c_release_client(struct i2c_client *client);

/* call the i2c_client->command() of all attached clients with
 * the given arguments */
extern void i2c_clients_command(struct i2c_adapter *adap,
                                unsigned int cmd, void *arg);

extern struct i2c_adapter *i2c_get_adapter(int nr);
extern void i2c_put_adapter(struct i2c_adapter *adap);
extern unsigned int i2c_adapter_depth(struct i2c_adapter *adapter);

void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);

/* Return the functionality mask */
static inline u32 i2c_get_functionality(struct i2c_adapter *adap)
{
        return adap->algo->functionality(adap);
}

/* Return 1 if adapter supports everything we need, 0 if not. */
static inline int i2c_check_functionality(struct i2c_adapter *adap, u32 func)
{
        return (func & i2c_get_functionality(adap)) == func;
}

/**
 * i2c_check_quirks() - Function for checking the quirk flags in an i2c adapter
 * @adap: i2c adapter
 * @quirks: quirk flags
 *
 * Return: true if the adapter has all the specified quirk flags, false if not
 */
static inline bool i2c_check_quirks(struct i2c_adapter *adap, u64 quirks)
{
        if (!adap->quirks)
                return false;
        return (adap->quirks->flags & quirks) == quirks;
}

/* Return the adapter number for a specific adapter */
static inline int i2c_adapter_id(struct i2c_adapter *adap)
{
        return adap->nr;
}

static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg)
{
        return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0);
}

int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr);
/**
 * module_i2c_driver() - Helper macro for registering a modular I2C driver
 * @__i2c_driver: i2c_driver struct
 *
 * Helper macro for I2C drivers which do not do anything special in module
 * init/exit. This eliminates a lot of boilerplate. Each module may only
 * use this macro once, and calling it replaces module_init() and module_exit()
 */
#define module_i2c_driver(__i2c_driver) \
        module_driver(__i2c_driver, i2c_add_driver, \
                        i2c_del_driver)

/**
 * builtin_i2c_driver() - Helper macro for registering a builtin I2C driver
 * @__i2c_driver: i2c_driver struct
 *
 * Helper macro for I2C drivers which do not do anything special in their
 * init. This eliminates a lot of boilerplate. Each driver may only
 * use this macro once, and calling it replaces device_initcall().
 */
#define builtin_i2c_driver(__i2c_driver) \
        builtin_driver(__i2c_driver, i2c_add_driver)

#endif /* I2C */

#if IS_ENABLED(CONFIG_OF)
/* must call put_device() when done with returned i2c_client device */
extern struct i2c_client *of_find_i2c_device_by_node(struct device_node *node);

/* must call put_device() when done with returned i2c_adapter device */
extern struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node);

/* must call i2c_put_adapter() when done with returned i2c_adapter device */
struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node);

extern const struct of_device_id
*i2c_of_match_device(const struct of_device_id *matches,
                     struct i2c_client *client);

#else

static inline struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
{
        return NULL;
}

static inline struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
{
        return NULL;
}

static inline struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node)
{
        return NULL;
}

static inline const struct of_device_id
*i2c_of_match_device(const struct of_device_id *matches,
                     struct i2c_client *client)
{
        return NULL;
}

#endif /* CONFIG_OF */

#if IS_ENABLED(CONFIG_ACPI)
u32 i2c_acpi_find_bus_speed(struct device *dev);
#else
static inline u32 i2c_acpi_find_bus_speed(struct device *dev)
{
        return 0;
}
#endif /* CONFIG_ACPI */

#endif /* _LINUX_I2C_H */